For a complete description of port modes, administrative states, and operational states, see the ''[http://www.cisco.com/en/US/docs/switches/datacenter/sw/6_x/nx-os/interfaces/configuration/guide/if_cli.html Cisco NX-OS Interfaces Configuration Guide]''.

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== Port Guidelines ==

== Port Guidelines ==

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Use the '''show interface''' command to verify the state of the interface. See the ''[http://www.cisco.com/en/US/docs/switches/datacenter/sw/4_0/nx-os/interfaces/configuration/guide/if_nxos_book.html Cisco NX-OS Interfaces Configuration Guide, Release 4. 0]'' for reasons why a port may be in a down operational state.

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Use the '''show interface''' command to verify the state of the interface. See the ''[http://www.cisco.com/en/US/docs/switches/datacenter/sw/6_x/nx-os/interfaces/configuration/guide/if_cli.html Cisco NX-OS Interfaces Configuration Guide]'' for reasons why a port may be in a down operational state.

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* '''show udld '''

* '''show udld '''

* '''show tech-support udld'''

* '''show tech-support udld'''

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== Troubleshooting Port States from the CLI ==

== Troubleshooting Port States from the CLI ==

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The following links contain further information on this topic from Cisco.com:

The following links contain further information on this topic from Cisco.com:

Information About Troubleshooting Ports

Before a switch can relay frames from one data link to another, the characteristics of the interfaces through which the frames are received and sent must be defined. The configured interfaces can be Ethernet interfaces, the management interface (mgmt0), or VLAN interfaces (SVIs).

Each interface has an associated administrative configuration and operational status as follows:

The administrative configuration does not change unless you modify it. This configuration has various attributes that you can configure in administrative mode.

The operational status represents the current status of a specified attribute like the interface speed. This status cannot be changed and is read-only. Some values may not be valid when the interface is down (such as the operation speed).

Port Guidelines

Follow these guidelines when you configure a port interface:

Before you begin configuring a switch, make sure that the modules in the chassis are functioning as designed. Use the show module command to verify that a module is OK or active before continuing the configuration.

When configuring dedicated ports in a port group, follow these port mode guidelines:

You can configure only the one port in each four-port group in dedicated mode. The other three ports are not usable and remain shut down.

If any of the other three ports are enabled, you cannot configure the remaining port in dedicated mode. The other three ports continue to remain enabled.

License Requirements

There are no licensing requirements for port configuration in Cisco NX-OS.

Initial Troubleshooting Checklist

Begin troubleshooting the port configuration by checking the following issues:

Checklist

Check off

Check the physical media to ensure that there are no damaged parts.

Verify that the SFP (small form-factor pluggable) devices in use are those authorized by Cisco and that they are not faulty.

Verify that you have enabled the port by using the no shutdown command.

Verify that you have configured a port as dedicated and make sure that you have not connected to the other three ports in the port group.

Viewing Port Information

You can use the show interface counters command to view port counters. Typically, you only observe counters while actively troubleshooting, in which case you should first clear the counters to create a baseline. The values, even if they are high for certain counters, can be meaningless for a port that has been active for an extended period. Clearing the counters provides a better idea of the link behavior as you begin to troubleshoot.

Use one of the following commands to clear all port counters or the counters for specified interfaces:

clear counters interface all

clear counters interfacerange

The counters can identify synchronization problems by displaying a significant disparity between received and transmitted frames.

Use the following commands to gather more information about ports:

show interface status

show interfaces capabilities

show udld

show tech-support udld

Troubleshooting Port States from the CLI

To display complete information for an interface, use the show interface command. In addition to the state of the port, this command displays the following:

Port-Interface Issues

This section includes symptoms and solutions for troubleshooting ports.

You Cannot See The Interface

You may have a problem where an interface does not show up on your device because of the VDC configuration.

Symptom

Possible Cause

Solution

You cannot see the interface.

The interface has been allocated to a different VDC.

Log in as network-admin and use the show vdc membership command to determine which VDC owns the interface.

The Interface Configuration Has Disappeared

You may have a problem where your interface configuration disappears.

Symptom

Possible Cause

Solution

The interface configuration has disappeared.

The interface was reallocated to a different VDC.

Cisco NX-OS removes the interface configuration when you reallocate an interface to a different VDC. You must reconfigure the interface.

The interface mode has changed to or from the switchport mode.

Cisco NX-OS removes the interface configuration when you switch between Layer 2 and Layer 3 port mode. You must reconfigure the interface.

You Cannot Enable an Interface

You may have a problem when enabling an interface.

Symptom

Possible Cause

Solution

You cannot enable an interface.

The interface is part of a a dedicated port group.

You cannot enable the other three ports in a port group if one port is dedicated. Use the show running-config interface CLI command to verify the rate mode setting.

The interface configuration is incompatible with a remote port.

Use the show interface capabilities command on both ports to determine if both ports have the same capabilities. Modify the configuration as needed to make the ports compatible.

The Layer 2 port is not associated with an access VLAN or the VLAN is suspended.

Use the show interface brief command to see if the interface is configured in a VLAN. Use the show vlan brief command to determine the status of the VLAN. Use the state active command in VLAN configuration mode to configure the VLAN as active.

An incorrect SFP is connected to the port.

Use the show interface brief command to see if you are using an incorrect transceiver. Replace with a Cisco-supported SFP.

You Cannot Configure a Dedicated Port

You may have a problem when trying to configure a port as dedicated.

Symptom

Possible Cause

Solution

You cannot configure a dedicated port.

The other three ports in the port group are not shut down.

Use the shutdown command in interface configuration mode to disable the other three ports in the port group.

One or more of the other three ports in the port group are not configured in the same VDC.

Use the show vdc membership command to find out which ports are in a different VDC.

The port is not the first port in the port group.

You can only set the first port in a port group to the dedicated mode.

A Port Remains in a Link Failure or Not Connected State

You may have a problem with ports or links becoming operational.

Symptom

Possible Cause

Solution

A port remains in a link-failure state.

The port connection is bad.

Use the show port internal info command to verify the port status is in link-failure.

Verify the type of media in use. Is it copper or optical, single-mode (SM), or multimode (MM)?

Verify that the media is not broken or damaged. Is the LED on the switch green?

Use the shutdown command followed by the no shutdown command to disable and enable the port. If this problem persists, try moving the connection to a different port on the same or another module.

There is no signal because of a transit fault in the small form-factor pluggable (SFP) or the SFP may be faulty.

When this problem occurs, the port stays in a transit port state and you see no signal. There is no synchronization at the MAC level. The problem may be related to the port speed setting or autonegotiation. Verify that the SFP on the interface is seated properly. If reseating the SFP does not resolve the issue, replace the SFP or try another port on the switch.

The link is stuck in the initialization state or the link is in a point-to-point state.

Use the show logging command to check for a "Link Failure, Not Connected system" message.

Use the shutdown command followed by the no shutdown command to disable and enable the port. If this problem persists, try moving the connection to a different port on the same or another module.

An Unexpected Link Flapping Occurs

When a port is flapping, it cycles through the following states, in this order, and then starts over again:

Initializing-The link is initializing.

Offline-The port is offline.

Link failure or not connected-The physical layer is not operational and there is no active device connection.

When you are troubleshooting an unexpected link flapping, you should know the following information:

Who initiated the link flap.

The actual link down reason.

Symptom

Possible Cause

Solution

An unexpected link flapping occurs.

The bit rate exceeds the threshold and puts the port into the errDisabled state.

Use the shutdown command followed by the no shutdown command to return the port to the normal state.

A problem in the system triggers the link flap action by the end device. Some of the causes are as follows:

A packet drop in the switch occurs, because of either a hardware failure or an intermittent hardware error such as an X-bar sync loss.

A packet drop results from a software error.

A control frame is erroneously sent to the device.

Determine the link flap reason as indicated by the MAC driver. Use the debug facilities on the end device to troubleshoot the problem. An external device may choose to reinitialize the link when it encounters the error. In such cases, the method of reinitializing the link varies by device.

A Port Is in the ErrDisabled State

The ErrDisabled state indicates that the switch detected a problem with the port and disabled the port. This state could be caused by a flapping port or a high amount of bad frames (CRC errors), which could indicate a problem with the media.